1. Field
The invention is directed toward waveguide transitions, broadband antennas, and methods of their use. Specifically, the invention is directed toward double-ridged waveguide launchers and horn antennas.
2. Background
Broadband horn antennas are of significant interest in a number of test and measurement applications, as well as communication links, commercial and military radars, and scientific instrumentation. Many successful designs based on double-ridged geometry have been demonstrated in the cm-wave frequency band. Horns up to 18 GHz are especially common and readily available for purchase from commercial vendors. Very few such broadband horns, however, have extended much in to the millimeter-wave range, though some have been reported and are even commercially available at frequencies up to about 40 GHz. Among the challenges that make higher-frequency broadband implementations difficult is the launcher itself—that is, the broadband transition from coax or other Transverse Electric and Magnetic (TEM) transmission-line to the balanced double-ridged waveguide in the throat of the horn—and the avoidance of mode-resonances in the taper from the throat of the horn to the radiating aperture. Both of these tasks are made much harder by the relatively poor fabrication tolerance that is inevitably encountered at higher frequencies where the relevant structural features become microscopically small.